This invention relates generally to power window systems and methods for controlling a power-operated window, and more particularly to a power window system or electric-motor driven mechanism which electrically actuates a regulator (windowpane lift mechanism) to open and close a window (lower and raise a windowpane or window glass) of a vehicle.
Many vehicles are equipped with a power window system in recent years. The power window system is adapted to move down and up a windowpane (to open and close a window) provided in each door of a vehicle, by switching rotation of a motor between normal and reverse directions. Typically, activation of an OPEN switch causes a DOWN motion of a relevant windowpane toward a fully opened position, while activation of a CLOSE switch causes an UP motion of a relevant windowpane toward a fully closed position. In such a power window system, during an automatic upward movement (AUTO-UP motion) of a windowpane, triggered by an activation of a CLOSE switch and continued with a driving force (mechanical power) provided by a motor, an obstacle may happen to come in a gap between an upper edge of the windowpane and an upper sash of the door (or roof side rail of the vehicle in an instance where the window is sashless) and possibly be trapped in the gap as the windowpane moves up.
With this in view, various considerations have been taken into account in order to prevent an obstacle trapping accident; for example, disclosed in JP 2000-87645 A is a power window system in which a motor is reversed (reversely rotated) to immediately lower the windowpane when the obstacle is accidentally placed through the window and caught in a gap between an upper edge of the windowpane and an upper sash of the door (or roof side rail of the vehicle in an instance where the window is sashless) during closing operation (while the windowpane is rising). In operation, to be more specific, this system is configured to detect that the obstacle is trapped (hereinafter referred to “trap detection”), if an excess load placed to the motor due to the obstacle trapped in the window increases a driving voltage applied to the motor beyond a predetermined threshold.
On the other hand, to render the discussion complete, consideration may have to be given to the fully closed position of the windowpane in conjunction with the trap detection during closing operation of the window (while the windowpane is rising), in that the trap detection would occur in response to the load that could be placed to the motor when the windowpane has risen to the fully closed position, which would cause the motor to be reversed (reversely rotated), and thus lower the windowpane even if no obstacle is trapped in the window, with the result that one would become unable to fully close the window.
For this reason, a rotation sensor, for example, composed of a Hall element, may be provided in the motor. The rotation sensor outputs a pulse signal corresponding to the rotation of the motor, and pulses of the output pulse signal are counted, to determine the position of the windowpane. If thus-determined position of the windowpane shows that the windowpane has reached the fully closed position, the rotation of the motor is stopped. To establish this setup, at the outset (initial stage of learning), the position of the windowpane that has been fully closed is determined as a reference position, and the number of pulses (pulse count value) corresponding to the reference position is memorized for use in future position measurement as a reference, so that the position of the windowpane can be accurately measured at any time even after the window has been opened and closed repeatedly (i.e., windowpane has been moved down and up a good many times, and stopped or switched back halfway at times).
The pulse count value corresponding to the reference position acquired at the initial stage of learning may be stored in a nonvolatile memory, such as an electrically erasable programmable read only memory or EEPROM, so as to protect against unintentional erasure of the data of the pulse count value in anticipation of a replacement of a battery installed in the vehicle and a voltage drop of the battery below a permissible level during startup of the engine or under other circumstances.
Meanwhile, if the voltage of the battery installed in the vehicle drops below a predetermined level (e.g., 9V) during the opening and closing operations of the window for some reason, the rotation of the motor which causes the windowpane to move up and down is stopped, and the position of the windowpane at that time should be stored in a memory.
In this situation, allowance may have to be made for the inertia of the windowpane which causes the motor to coast around for a little while after the motor is stopped, and when the upward or downward movement of the windowpane is stopped in actuality, the motor has turned slightly past the position expected at the instant when the motor is stopped. Accordingly, it is contemplated that the position of the windowpane to be stored in the memory may preferably be measured after the lapse of a sufficient period of time, e.g., 200 ms or so, in order to prevent an error in position of the windowpane. For that purpose, however, a large-capacitance capacitor capable of supplying energy much enough for writing operation into the memory would disadvantageously be required under the conventional scheme, leading to an undesired increase in the cost of implementing the system.
It would thus be desirable to provide a power window system and a method for controlling a power-operated window, in which the position of a windowpane that has been stopped when the voltage of a battery drops below a predetermined level during opening or closing operation of the window is stored in a memory without using a large-capacitance capacitor, and an error in the position of the windowpane is prevented.
Illustrative, non-limiting embodiments of the present invention overcome the above disadvantages and other disadvantages not described above. Also, the present invention is not required to overcome the disadvantages described above, and an illustrative, non-limiting embodiment of the present invention may not overcome any of the problems described above.